Specifically, the problem with the 2006 loans was not that this vintage included more loans with adjustable rates, zero down payments and reduced documentation (though it did). The problem with the 2006 vintage was that loans with adjustable rates, zero down payments and reduced documentation performed drastically worse in 2006 than otherwise identical loans earlier. What was the factor that caused so many defaults among the later loans? One possibility is that the loans were worse on dimensions that are unobservable to the econometrician. Another possibility is that the earlier loans were made when house prices were rising, while the 2006 loans were made just as prices were beginning to fall.
Pointer from Greg Mankiw, who indicates that the piece may soon fall behind a paywall.
I view this as reinforcing my bias, which is to treat mortgage default as primarily a function of (negative) housing equity, and only secondarily borrower risk characteristics. All sorts of bad loans looked fine as long as home prices were rising. In my view, the big mistake was to pile on more and more high-LTV loans, which could only be safe if prices continued to rise.
Later, they write,
The question of whether the subprime crisis resulted from insider/outsider conflicts or a classic asset bubble has important implications for public policy. If insider/outsider conflicts are responsible, then regulators should try to align the incentives of borrowers and lenders and/or protect borrowers from unfair practices. Along these lines, the Dodd-Frank Wall Street Reform and Consumer Protection Act, passed by Congress in 2010 as a wide-ranging response to the financial crisis, established the Consumer Financial Protection Bureau to promulgate regulations for mortgages, credit cards and other financial products.
Yes. And as they point out, the narrative that this was a case of lenders and securitizers taking advantage of consumers and investors does not hold up well. Instead, it was a case of consumers and investors fooling themselves into believing that outcomes which depended on persistent house price appreciation would continue forever.